The present invention relates to fastening systems and, more specifically, to a system using a self-penetrating fastener for forming a riveted joint.
A nail gun is a well-known fastening tool that injects nails fed from a supply into a structural material such as wood. Nail guns are commonly powered by compressed air or electricity. Using a nail gun, a worker can easily form hundreds of nailed joints per hour.
It is often desirable to join structures that are difficult to nail, such as hard materials, fragile materials, or thin sheets of material such as sheet metal. Rivets are commonly used to fasten such materials.
Although many types of rivets are known, they can be generally grouped into two categories: pull-type or "blind" rivets, and compression-type or "drive" rivets. The fastener of the present invention is similar to a blind rivet. Blind rivets comprise a rod-shaped stem having an enlarged mandrel frangibly connected to one end and a cylindrical body enclosing a portion of the stem adjacent the mandrel. The body commonly has an enlarged flange or head at the end furthest from the mandrel.
To join workpieces using a blind rivet, a hole is drilled through the workpieces. The rivet stem is inserted into the nosepiece of a riveting tool, which firmly grasps the rivet stem. The rivet mandrel is then inserted into the hole through the workpieces so that the cylindrical portion of the body extends completely through the hole and the head rests against one of the workpieces. The riveting tool, restraining the rivet head against motion relative to the workpieces, applies a pulling force to the stem such that the mandrel, which has a slightly greater diameter than the inside diameter of the body, is pulled into the body, expanding it radially, and thereby forming an enlarged mushroom-shaped head on the "blind" side of the workpieces. The stem is then broken off from the mandrel by further pulling and is discarded.
Both portable, hand-held riveting tools and permanently mounted riveting machines suitable for production-line assembly are known. Riveting tools may be powered by compressed air or electricity.
Although riveting can form strong joints, it is a relatively slow and labor-intensive fastening method because a hole must be drilled through the workpieces before each rivet is installed. Prior art riveting methods therefore require two tools: a drill and a riveting tool. Although using two tools in an alternating fashion is inconvenient, inefficient, and uneconomical in any assembly situation, these problems are especially evident in situations where hand-held tools are used, such as in the construction industry. A worker must carry both the drill and the riveting tool as he works along large sections of metal sheathing or ductwork. Each time the worker moves to a new position, he must pick up the drill, drill a hole, put the drill down, pick up the riveting tool, install the rivet, and put the riveting tool down. Repeatedly performing these steps is tedious, tiring, and inefficient. These problems and deficiencies are clearly felt in the art and are solved by the present invention in the manner described below.